The purpose of this research is to determine the mechanism of estrogen action in causing a decrease in progesterone secretion (luteolysis) in the primate. This will be accomplished by studying the pharmacologic effects of estradiol-17 beta on corpus luteum progesterone secretion and to determine its role in causing the release of PGF from the uterus and/or ovary. It is therefore hypothesized that the luteolytic effect of estrogen in the primate is mediated by a local release of PGF. Acute surgical studies will be performed during the luteal phase of the menstrual cycle with and without the prostaglandin inhibitor, indomethacin, to observe the effect of estradiol infusion on ovarian and uterine venous PGF content and ovarian venous steroid concentrations (estradiol and progesterone). This surgical approach, cannulation of the uterine and ovarian veins, will be taken because prostaglandins E and F have been shown to be rapidly metabolized after one pass through the circulation. Peripheral levels are therefore obscure and have not been found to differ significantly during the normal menstrual cycle. Also this surgical model will determine the site of prostaglandin release.